The invention relates to rail-mounted automatic electrical switches which are intended for limited-space applications.
The applicant is commercially marketing a similar automatic switch under the name "Sursum Typ EA." In this known small automatic switch, the mounting device is comprised of two mutually facing hooks disposed at a distance from each other, one of which hooks is spring-loaded. Both hooks extend behind parallel mounting-rail edges, engaging them from their outer surfaces. The second hook is pushed over its corresponding rail edge while the first one is undergoing a spring-loaded retraction. Both electrical terminals in this switch are of the screw-clamp type (binder posts). These two screw clamps are wired to the external circuit leads following the actual mounting of the automatic switch on the rails. Experience has shown that these mounting steps are costly.
It is therefore an object of the invention to devise an automatic switch of the type described supra, and particularly to modify the "Sursum Typ EA" automatic switch, such that one of the three mounting steps is eliminated. This object is achieved by the invented automatic switch in that one of the mounting devices also serves as a terminal which is connected to one of the electrical leads, and in that the other mounting device consists of a separate snap-action holding means disposed at a distance from said mounting terminal. Thus, one electrical connection is achieved with the mounting of the automatic switch on the rails, one of which is a conductor. Therefore, only two mounting steps in all are required, namely, the mounting onto the rails and the wiring of the second screw clamp.
A known mounting device (U.S. Pat. No. 2,842,635) comprised of a plug contact and a separate snap-action holding element could be employed with an automatic switch of the type described supra, in particular the "Sursum Typ EA," so that that class of switch might contain a plug terminal which could be snapped onto a current-carrying rail. In this way, a miniature automatic switch could be made compatible with the advantageous and widely used system wherein switch supports consist of rails, with one of said rails being current-carrying. This combination of the "Sursum Typ EA" with the known mounting device would be nonobvious to one of ordinary skill in the art because it entails a number of major alterations to the structure of the known automatic switch. In place of the rail upon which the additional snap-action holding element is engaged, another engaging piece could be provided, e.g., a dog or spring-loaded detent.
If the bimetallic thermal tripping element, the switch mechanism, and the switch contacts of the "Sursum Typ EA" are moved toward one lateral side, and the hand lever and the impact-armature tripping device are moved toward the other lateral side, it would be particularly advantageous if the plug terminal could be arranged on the first-mentioned lateral side, and the additional snap-action holding element arranged on the other lateral side. This positioning of the plug terminal is advantageous in the context of the overall arrangement of components in the housing, in contrast to the known switch.
If a support strip bearing the bimetallic thermal tripping element were to be anchored to a lateral face of the housing, it would be particularly advantageous if the plug terminal, which should pass through an opening in the the rear of the housing, lockingly could engage a side of the housing and could be electrically connected to the metallic support strip inside the housing. The support strip already present in the known automatic switch could thus be employed, and the plug terminal would require less housing interior space while still being securely held.